1. Technical Field
This invention relates to a device for transmitting and receiving electromagnetic waves. More particularly, this invention relates to a high gain omnidirectional antenna. Specifically, this invention relates to a series fed omnidirectional antenna formed via collinear cone elements which are phased using external elements angled with respect to the overall longitudinal axis of the antenna. Further, this invention relates to incorporating a dome shaped ground plane element into the overall series fed omnidirectional antenna design.
2. Background Information
The standard series-fed collinear high gain omnidirectional antenna design has several undesirable characteristics such as a distinctly narrowed frequency range. This narrowed frequency range applies to gain, standing wave radio (SWR), and overall pattern. The primary elevation coordinate signal pattern drops well below the horizon with frequency decreasing below the optimal tuned frequency. Conversely, corporate-fed coaxial dipoles seen for decades mounted on towers and masts, maintain the elevation coordinate signal pattern near the horizon at all tuned frequencies. While the series-fed collinear designs occupy a small horizontal space, typically contained in a vertical tube made of fiberglass, corporate fed coaxial dipoles around a mast or tower take up an enormous amount of horizontal space. This leads to problems with wind shear and elements as a fiberglass tube generally is not available for protection from the elements for such a large horizontal structure.
More recent designs have attempted to combine the smaller lateral dimension advantage of standard series-fed collinear antennas with the broader frequency range maintained near horizon of the standard horizontally spaced corporate-fed omnidirectional antennas. Inasmuch as there are increasing needs for broader frequency band antennas, there is a tremendous need in the art for antennas which have reliably broader frequency ranges.
As seen in U.S. Pat. No. 6,057,804, and in particular, FIGS. 11 and 12, one significant design issue with corporate-fed coaxial dipoles relates to incorporating the complex feed system into the overall antenna design. The disclosure of U.S. Pat. No. 6,057,804 incorporates cylindrical element dipoles of substantially larger diameter such that the corporate-fed system has room inside the center of these stacked cylindrical dipoles for encapsulating the feed system. One will readily recognize this design is inherently very complex and involves an exponentially increasing number of connections as the input signal is split for each cylindrical dipole added.
There have been attempts to recognize the broad frequency band characteristics of the cone-style element and incorporate such cone-style into a corporate fed design. As shown in U.S. Pat. No. 7,855,693, and in particular, FIGS. 1 and 2, this design does not alleviate the complexity of powering each coned element. This can be further shown in U.S. Pat. No. 5,534,880, and in particular FIG. 2.